The ATM gene, mutated in ataxia telangiectasia (AT) has been identified by positional cloning. The discovery of ATM may soon allow the identification of AT heterozygotes, who may be at increased risk of cancer. Specific aims of this study are to identify factors motivating parents to pursue the possibility of carrier testing for their children; to assess psychological functioning, in order to identify problems to be addressed in testing programs. The sample of AT parents and siblings has thus far been drawn from UCLA (Dr. Richard Gatti), the A-T Children's Project (Brad Margus) and is being expanded to include the A-T Clinical Center at Johns Hopkins (Dr. Jerry Winkelstein). IRB approvals have been obtained, the semi-structured interview guide and questionnaires developed. Fifty eight individuals have been interviewed in their homes or over the phone, and interviews have been taped and are being typed verbatim; standard scales of anxiety and depression are being administered. Preliminary results indicate that 1) parents are overwhelmed with the care of the A-T child and do not focus on their own possible health concerns as obligate carriers; 2) siblings are often enlisted as home care caregivers, with profound neglect on their own developmental issues; 3) fathers and mothers cope very differently with having a disabled child, with troubling implications for their relationship; 4) families need psychological support, especially at the time of the diagnosis, to understand the disorder and its genetic implications.